The ambitious group has created more than 700 panoramas to date, shooting out of vehicles ranging from light jets and hot air balloons to radio-controlled helicopters.

Photoflights

Each AirPano photography trip usually takes around a week, involving several "photoflights," says Sergey Semenov, one of the photographers who shot the Manhattan panorama.

"We did several trips to NYC last year, each time shooting from helicopters or rooftops and hotel rooms," he tells CNN.

The 29-year-old Russian worked as an economist, but now spends most of his time on the road -- and in the air -- for his photography projects, including those for AirPano.

"There's no business model," says Semenov. "We just do it for fun, as a hobby. On our own resources."

The stitching and retouching of the virtual tours takes another week or two after the photoflights are completed.

Then the virtual tour is uploaded online, consisting of five to 12 panoramas, a story, photos and behind-the-scenes videos.

Manhattan obsession

The Manhattan tour was particularly mesmerizing for the photographers. Each building can be singled out in a sea of jam-packed skyscrapers.

"Traditionally, New York City and Manhattan attract a lot of visitors to our site," says Semenov.

"Almost all of our virtual tours and separate panoramas over Manhattan are in the top 10 or top 20 of the most visited tours -- especially these that I shot two years ago in a room of the U.N. Millennium Plaza Hotel."

The reception has been overwhelmingly positive, with the number of unique visitors to the website reaching 80,000 per day and half a million on the best traffic days.

Semenov's most recent panorama project was an erupting volcano in Kamchatka, Russia, which he shot with another photographer during the last two weeks of December 2012.

"It's a mixture of art and entertainment and education," says Semenov.

"We are classical landscape photographers who really love to travel. So we always try to show it as beautifully and with as much informative detail as we can."